JPH0652706B2 - Projection exposure device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus, and particularly in the field of semiconductor device manufacturing, automatic focus adjustment when repeatedly reducing and projecting a reticle circuit pattern onto a semiconductor wafer surface. The present invention relates to a projection exposure apparatus called a stepper having a so-called autofocus function.

<Prior Art> In recent years, an image forming (projection) optical system having a high resolving power is required in a projection exposure apparatus due to a demand for finer patterns and higher integration of semiconductor elements, LIS elements, VLSI elements, and the like. As a result, the NA of the image forming optical system is increasing, and the depth of focus of the image forming optical system is becoming shallower.

In addition, the wafer must be allowed to have a certain degree of variation in thickness and bending in terms of planar processing technology. In order to correct the bending of the wafer, the wafer is placed on a wafer chuck that is processed so as to guarantee flatness on the order of subcyclones, and the back surface of the wafer is vacuum-sucked to correct the flatness. However, it is impossible to correct the variation in the thickness of one wafer, the suction method, and the deformation of the wafer caused by the progress of the process, no matter how much the plane of the wafer is corrected.

Therefore, since the wafer has irregularities in the screen area where the reticle pattern is projected by reduction projection, the effective depth of focus of the optical system is further reduced.

Therefore, in the reduction projection exposure apparatus, an effective automatic focusing method for matching the wafer surface with the focal plane (the image plane of the projection optical system) is an important theme.

As a wafer surface position detection method of a conventional reduction projection exposure apparatus, a method using an air microsensor, and a method in which a light beam is incident on a wafer surface from an oblique direction without passing through a projection exposure optical system,
A method (optical method) for detecting the amount of displacement of the reflected light is known.

On the other hand, in this type of projection exposure apparatus, the focus position changes due to a change in the ambient temperature of the projection optical system, a change in atmospheric pressure, a temperature rise due to the light beam illuminating the projection optical system, or a temperature rise due to heat generation of the apparatus including the projection optical system. (Image plane position) moves and must be corrected. Therefore, the focus position of the projection optical system can be calculated by measuring the ambient temperature change and atmospheric pressure change with a detector, or by measuring the temperature change of a part of the projection optical system and atmospheric pressure change detector. I was making corrections.

However, in this method, since the focus position of the projection optical system is not directly measured, the focus position of the projection optical system is determined from the detection error of the detector that measures the temperature and atmospheric pressure, and the temperature change amount and the atmospheric pressure change amount. There is a drawback in that it is impossible to detect the focus position of the projection optical system with high accuracy due to an error included in a calculation formula that is an approximate formula when calculating and correcting the.

<Outline of the Invention> An object of the present invention is to focus a position (image plane position) of a projection optical system.
It is an object of the present invention to provide a projection exposure apparatus capable of accurately detecting the laser beam and accurately matching the image plane of the projection optical system with the wafer surface.

In order to achieve the above object, the present projection exposure apparatus that projects a pattern formed on a first object onto a second object via a projection optical system includes a movable stage that holds the second object, A reflecting surface provided on the movable stage, means for directing light onto the reflecting surface via the pattern and the projection optical system, and light received from the reflecting surface via the projection optical system and the pattern However, it is characterized by having a light amount detecting means for detecting a light amount and a means for detecting a focus position of the projection optical system based on a signal from the light amount detecting means.

Specific embodiments of the present invention are described in detail in the examples below, and particularly preferred embodiments of the present invention were constructed based on the following five basic ideas. Further, the image plane position of the projection optical system, that is, the focus position is determined by using the projection optical system itself (so-called TTL system) as described above. In addition, "TT
“L” is an abbreviation for “Through The Lens”.

(1) The focus position (image plane of the projection optical system) is detected directly at the exposure wavelength.

(2) An illumination system used for exposure is used to detect the focus position.

(3) The focus position is detected by using the reticle used for printing.

(4) The focus position detection position basically matches the wafer detection position in the off-axis method that does not use the conventional projection optical system.

(5) A reference reflection surface on which a resist or the like is not applied is provided on the wafer stage for detecting the focus position.

It can be said that the most ideal form is to detect the focus using the wavelength of the light actually used for exposure, the illuminator, and the reticle. If the wavelength is different from that of the exposure light, the atmospheric pressure-focus characteristics and the exposure-focus characteristics of the projection optical system (lens system) are slightly different, and it is necessary to perform offset correction by calculation. Such a correction causes an error, and it is impossible to describe all the phenomena only by calculation.
Here, there are two drawbacks in using the exposure wavelength for the probe light of TTL focus. One is that the exposure light exposes the resist, and the other is that when a process such as a multilayer resist or an absorption resist is adopted on the wafer side, the reflected light from the wafer does not return. Therefore, the present invention solves this problem by forming the reference reflecting surface on the wafer stage. By measuring the position of this reference reflection surface with both the conventional off-axis autofocus system and the TTL autofocus system, the correspondence between the two is achieved. For that reason,
As described in (4), the detection positions of the two need not be exactly the same, but basically they must be the same. Further, since the conventional off-axis autofocus system uses a non-exposure wavelength, it is free from the problems associated with multilayer resists and the like.

The most typical TTL autofocus method is to project a slit image on a wafer surface through a projection lens and receive the reflected light again through the slit. It determines the position of the waste. For example, it is known that a slit for this kind is provided in an observation microscope to project and the amount of received light is taken.

In this type of imaging, the most accurate imaging is performed between the reticle and the wafer at the exposure wavelength. Moreover, the reticle has a fine pattern for LSI manufacturing. Therefore, it is not necessary to specially provide a slit for detecting a focus error in the microscope system, and a focus error signal can be sufficiently obtained by utilizing a fine pattern of the reticle itself.

In the projection exposure apparatus having such a configuration, the exposure light from the illumination optical system is directed to the reticle while the reticle (mask) having the circuit pattern is mounted on the stage, and the light passing through the reticle is passed through the projection optical system. To the reference reflection surface on the wafer stage. Then, the reflected exposure light from the reference reflection surface is returned again to the illumination optical system via the projection optical system and the reticle, and this reflected exposure light is received by the light receiving element. The output signal from this light receiving element is the focus error signal, and the wafer stage is moved up and down in the optical axis direction of the projection optical system to change the position of the reference reflecting surface. By detecting the position of the reference reflecting surface showing the value, this position can be known as the optimum focus position (best image plane position) of the projection optical system. In addition, by monitoring the position of this reference reflection surface with an off-axis autofocus system (wafer surface position detection system) that is separately provided, it is possible to track the focus position of the projection optical system over time and automatically Focus control, so-called autofocus, can be performed. That is, the optimum focus position of the projection optical system detected by the TTL autofocus system is used as the reference position of the off-axis autofocus system, and when actually processing a wafer, the off-axis autofocus system is used to adjust the reference position to this reference position. The amount of positional deviation of the wafer surface (or the amount of positional deviation of each shot area on the wafer) may be detected and corrected.

Specific examples will be shown below.

<Embodiment> FIG. 1 is a conceptual diagram showing a configuration of a reduction projection exposure apparatus having an automatic focus control apparatus according to an embodiment of the present invention.

In the figure, 7 is a reticle, which is held on a reticle stage 70. The circuit pattern on the reticle 7 is reduced by ⅕ on the wafer 9 on the xyz stage 10 by the reduction projection lens 8 to form an image, and exposure is performed.
In FIG. 1, a reference plane mirror 17 whose upper surface and a mirror surface of the wafer 9 are substantially aligned is arranged at a position adjacent to the wafer 9. The reason why the reference surface mirror 17 is used instead of using the wafer coated with the actual resist is as described above.

Also, the xyz stage 10 is in the optical axis direction (z) of the projection lens 8.
Also, it can be moved in a plane orthogonal to this direction, and can of course be rotated around the optical axis.

The reticle 7 is illuminated in the screen area where the circuit pattern is transferred by the illumination optical systems shown in FIGS.

The light emitting portion of the mercury lamp 1 which is the light source for exposure is located at the first focal point of the elliptical mirror 2, and the light emitted from the mercury lamp 1 is condensed at the second focal point position of the elliptical mirror 2.
An optical integrator 3 with its light incident surface positioned at the second focal position of the elliptical mirror 2 is placed, and the light emitting surface of the optical integrator 3 forms a secondary light source. The light emitted from the optical integrator 3 forming the secondary light source is bent by 90 ° in the optical axis (optical path) by the mirror 5 via the condenser lens 4. Incidentally, 55 is a filter for selectively taking out light having an exposure wavelength, and 56 is a shutter for controlling exposure. The exposure light reflected by the mirror 5 passes through the field lens 6 and illuminates the screen area on the reticle 7 where the circuit pattern is transferred. In this embodiment, the mirror 5 is configured to partially pass the exposure light such as 5 to 10%. The light that has passed through the mirror 5 reaches a photodetector 50 for monitoring fluctuations of the light source, etc., through a lens 52 and a filter 51 that transmits the exposure wavelength and cuts extra light for photoelectric detection.

In the figure, 11 to 12 form a known off-axis autofocus optical system. Reference numeral 11 denotes a light projecting optical system, and the light flux which is the non-exposure light emitted from the light projecting optical system 11 intersects the optical axis of the reduction projection lens 8. Reference plane mirror
It is assumed that the light is focused on a point on 17 (or the upper surface of the wafer 9) and reflected. The light flux reflected by the reference plane mirror 17 enters the detection optical system 12. Although illustration is omitted, a position detection light receiving element is arranged in the detection optical system 12, and the position detection light receiving element and the reflection point of the light flux on the reference plane mirror 17 are arranged so as to be conjugate. The positional deviation of the reduction projection lens 8 of the reference plane mirror 17 in the optical axis direction is detected by the detection optical system.
It is measured as the positional deviation of the incident light beam on the position detecting light receiving element in 12.

The positional deviation of the reference plane mirror 17 from the predetermined reference plane measured by the detection optical system 12 is transmitted to the autofocus control system 19. The autofocus control system 19 gives a command to the drive system 20 that drives the xyz stage 10 on which the reference plane mirror 17 is fixed. Also, when detecting the focus position by TTL, the auto focus control system 19 is a reference mirror.
17 near the predetermined reference position in the optical axis direction of the projection lens 8.
It shall be driven up and down in the (z direction). The position control of the wafer 9 at the time of exposure (the wafer 9 is arranged at the position of the reference plane mirror 17 in FIG. 1) is also performed by the autofocus control system 19.

Next, the focus position detection optical system of the reduction projection lens 8 according to the present invention will be described.

2 and 3, 7 is a reticle and 21 is a reticle 7.
The pattern portion formed above has a light shielding property.
Reference numeral 22 is a light-shielding portion sandwiched between the pattern portions 21. Here, when the focus position (image plane position) of the reduction projection lens 8 is detected, the xyz stage 10 moves in the optical axis direction of the reduction projection lens 8.

It is assumed that the reference plane mirror 17 is positioned on the optical axis of the reduction projection lens 8 and the reticle 7 is illuminated by the illumination optical systems 1-6.

First, the case where the reference plane mirror 17 is on the focus surface of the reduction projection lens 8 will be described with reference to 1 in FIG. The exposure light passing through the transmission part 22 on the reticle 7 is condensed and reflected on the reference plane mirror 17 via the reduction projection lens 8. The reflected exposure light follows the same optical path as the outward path,
The light is focused on the reticle 7 via the reduction projection lens 8 and passes through the light transmitting portion 228 between the pattern portions 21 on the reticle 7. At this time, the exposure light does not cause vignetting on the pattern portion 21 on the reticle 7, and the entire light flux passes through the transmissive portion of the pattern portion 21.

Next, a case where the reference plane mirror 17 is located at a position displaced from the focus surface of the reduction projection lens 8 will be described with reference to FIG. The exposure light passing through the transmission part of the pattern part 21 on the reticle 7 reaches the reference plane mirror 17 through the reduction projection lens 8, but the reference plane mirror 17 is not on the focus surface of the reduction projection lens 8, The exposure light is reflected by the reference plane mirror 17 as a spread light beam. That is, the reflected exposure light follows an optical path different from the outward path, passes through the reduction projection lens 8, and is not condensed on the reticle 7, and is a reference plane mirror.
A light beam having a spread corresponding to the amount of deviation from the focus surface of the 17 reduction projection lens 8 reaches the reticle 7.
At this time, a part of the exposure light is eclipsed by the pattern portion 21 on the reticle 7, and the whole light cannot pass through the light transmitting portion 22. That is, there is a difference in the amount of light reflected through the reticle when the focus surface is matched and when it is not.

The optical path after the luminous flux of the exposure light reflected by the reference plane mirror 17 has passed through the reticle 7 described in FIGS. 2 and 3 will be described with reference to FIG.

The exposure light transmitted through the reticle 7 passes through the field lens 6 and reaches the mirror 5. Since the mirror 5 has a transmittance of about 5 to 10% with respect to the exposure light as described above, a part of the exposure light reaching the mirror 5 passes through the mirror 5 and the field stop 14 via the imaging lens 13. On the surface of. At this time, the surface of the reticle 7 on which the pattern exists and the field stop 14 are in a conjugate position via the imaging lens 13.

The exposure light that has passed through the aperture of the field stop 14 has a condenser lens 15
The light enters the light receiving element 16.

A filter 51 that selectively transmits only the exposure light is arranged on the front surface of the light receiving element 16 if necessary, and an electric signal according to the amount of the incident exposure light is output.

Here, the operation of the field stop 14 will be described. The field stop serves to limit the detection area detected by the light receiving element 16. The detection area is basically configured to correspond to that of the off-axis focus optical system including 11 to 12, that is, to detect in the same area. However, if a rough pattern such as a scribe line is included in the detection area and its influence is dominant and there is a problem in detection sensitivity,
It is also possible to shift the position of 14 to make the influence of the signal from the fine pattern dominant. In such a case, the field stop 14 is designed to be able to control any or all of the position in the direction orthogonal to the optical axis direction, the size of the opening, the shape of the opening, etc., as shown in FIG. And good.
Also, it is conceivable that the movement of the entire optical system up to 15 to 16 as the movement of 14 is considered, but both of them are limited to the range where the position corresponds to the detection area of the off-axis autofocus optical system 11 and 12. . Further, when the detection area is limited by the shape of the light receiving element 16 itself, the field stop 14 is not always necessary. At this time, the light receiving element 16 is at a position conjugate with the reticle 7,
For example, it is arranged at the position of the field stop 14 in FIG.

A method of detecting the focus position (image plane position) of the reduction projection lens 8 using the signal output of the light receiving element 16 will be described below.

Xzy stage 1 with reference plane mirror 17 by drive system 20
It is assumed that 0 is driven in the optical axis direction of the reduction projection lens 8 around the zero point of measurement preset by the off-axis autofocus detection system 12. At this time, the position signal in the optical axis direction of the reference plane mirror 17 (autofocus measurement value z) measured by the autofocus detection system 12 at each position and the exposure light reflected by the reference plane mirror 17 are received by the light receiving element. Light is received at 16,
Focal plane (image plane) detection system 18 by converting to an electrical signal
The relationship of the outputs obtained from is as shown in FIG. At this time, the signal of the detection system 18 is corrected by the signal from the reference light amount detection system 53, for example, by normalizing the signal of the detection system 18 with the signal of the detection system 53, in order to eliminate the influence of the fluctuation of the light source 1. And

When the reference plane mirror 17 is located on the focus plane of the reduction projection optical system 8, the output of the focal plane detection system 18 shows a peak value. The autofocus measurement value z ₀ at this time is used as the focus position of the projection optical system 8 when the wafer 9 is exposed using the reduction projection lens 8. (Or, the focus position set in advance based on the measured value z ₀ is corrected.) The focus position of the projection lens 8 determined in this way becomes the reference position of the off-axis autofocus detection system. The actual best position for printing the wafer is a value obtained by offsetting the reference position from the reference position by taking into consideration the values such as the coating thickness of the wafer and the step amount. For example, when a wafer is exposed using a multi-layer resist process, only the uppermost portion of the multi-layer needs to be baked, so that the resist surface of the wafer and the reference position are substantially coincident with each other. On the other hand, when the exposure light reaches the substrate sufficiently with the single-layer resist, the focus of the wafer does not match the resist surface but the substrate surface. In this case, therefore, there is an offset of 1 μm or more between the resist surface and the reference position. Things are not rare. Such offset amount is unique to the process and is provided as an offset different from the projection exposure apparatus. It suffices for the apparatus itself to accurately obtain the focus position of the projection lens 8 itself by the method of the present invention, and the offset amount mentioned above is applied to the autofocus control system 19 and the drive system 20 only when necessary. It may be input in advance via a system controller (not shown) of the projection exposure apparatus.

The detection of the focus position z ₀ may be determined by the peak of the output of the focal plane detection system 18, but various other methods are possible. For example, to increase the detection sensitivity, a certain slice level 220
Is determined and the focus position is determined by knowing the autofocus measurement values z ₁ and z ₂ in the diagram showing the output of this slice level 220. Alternatively, a method such as obtaining the peak position using a differential method may be considered.

Also, in order to increase the detection resolution of the focus position z ₀ ,
As shown in FIG. 4, by moving the position of the field stop 14 (in some cases, the condenser lens 15 and the light-receiving element 16 together), the exposure light incident on the light-receiving element 16 is reduced in size. It may be considered to correspond to the light having passed through the translucent portion 22 having a width of the limit resolution line of No. 8.

The process of detecting the focus position of the reduction projection optical system 8 according to the present invention and exposing the wafer 9 is shown in the flowchart of FIG.

FIG. 6 shows a flowchart for detecting the focus position of the reduction projection optical system 8 for each wafer, but it is okay to detect the focus position for each shot, every few shots, and every few wafers. Needless to say.

Therefore, the reticle used for actual pattern transfer and the exposure light that passed through the projection lens are used as detection light, and the position of the wafer on which the pattern is transferred is detected, and the focus position of the projection lens is detected using the off-axis autofocus system. Can be directly measured to always position the wafer on which the pattern is to be transferred, on the focus surface of the projection lens.

Therefore, conventionally, in principle, a change in the focus position with time due to a temperature change around the projection exposure optical system, an atmospheric pressure change, or a temperature rise due to an irradiated light beam or a temperature rise due to heat generation of an apparatus including the projection optical system It has the advantage of not being affected.

In addition, there is an advantage in mounting that a focal plane (image plane) detection system of the projection optical system can be configured only by adding a simple and inexpensive imaging optical system, a condenser lens, and a light receiving element to the conventional illumination system.

Further, since the focus position measurement according to the present invention can be inserted at any time of the exposure cycle, there is an advantage that the time difference between the measurement and the exposure can be minimized.

FIG. 7 shows another embodiment of the present invention.

The reticle 7 that transfers the pattern to the wafer 9 may have different exposure areas to which the pattern is transferred in each process. Therefore, in an actual projection exposure apparatus,
In many cases, a so-called masking mechanism for illuminating an exposure area within a certain range, for example, an illumination area changing mechanism as disclosed in Japanese Patent Application Laid-Open No. 60-45252 by the present applicant is mounted.

FIG. 7 is the same as the embodiment described in FIG. 1 except for the illumination optical system. The illumination optical system will be described below.

The light emitting part of the mercury lamp 1 which is a light source for exposure is located at the first focal point of the elliptical mirror 2 and the light emitted from the mercury lamp 1 is focused on the second focal point of the elliptic mirror 2. There is. Three optical integrators having an incident surface thereof are placed at the second focal point position of the elliptical mirror 2, and the light emitted from the optical integrator 3 having the exit surface of the optical integrator 3 serving as a secondary light source is 23
After passing through the beam splitter 24 via the condenser lens of, the surface on which the illumination area changing mechanism of 25 exists is illuminated. Reference numeral 56 is a shutter, and 55 is a filter for limiting the exposure wavelength range as in FIG.

The illumination area changing mechanism 25 is formed of a diaphragm with a variable aperture, and has a function of passing only a partial area of the light flux illuminating the surface on which the illumination area changing mechanism 25 exists.

The beam splitter 24 has a property of transmitting the exposure light by about 90 to 95%.

The exposure light that has passed through the illumination area variable mechanism 25 is an imaging lens.
After passing through 26, the optical axis is bent 90 ° by the mirror 27, and after passing through the field lens 6, reaches the reticle 7. At this time, it is assumed that the surface on which the illumination area changing mechanism 24 exists via the imaging lens 26 and the field lens 6 and the surface on which the circuit pattern of the reticle 7 exists are arranged to be conjugate. Further, the entrance pupil of the reduction projection lens 8 interposed between the reticle 7 and the wafer 9 to be exposed is
It is configured to be conjugate with the exit surface of the optical integrator 4, and the circuit pattern surface of the reticle 7 is configured to be Koehler-illuminated by the illumination optical system shown by 1-3, 23-27, and 6 in FIG.

The exposure light used for focal plane detection passes through the pattern portion of the reticle 7, passes through the reduction projection lens 8, is reflected by the reference reflection mirror 17, passes through the reduction projection lens 8 again, and passes through the pattern portion of the reticle 7. The situation at this time is as described in FIGS. 2 and 3.

The exposure light transmitted through the transparent portion 22 of the reticle 7 again passes through the field lens 6 and is reflected by the mirror 27.
The light passes through the aperture of the illumination area changing mechanism 25 via the imaging lens 26. After this, the exposure light is reflected by the beam splitter 24 which reflects 5 to 10%, and then enters the light receiving element 16 by the condenser lens 28.

The subsequent method for detecting the focal plane is the same as that described in the embodiment of FIG.

The difference in FIG. 7 is that the beam splitter 24 replaces the mirror 5 in FIG. In this way, there is an advantage that the entire device can be made compact by attaching the illumination area changing mechanism. The beam splitter 24 also serves as a light guide to the photodetector 50 for monitoring the amount of exposure light. Further, the photodetector 50 is also used as a photodetector for detecting the integrated light amount during the circuit pattern projection exposure,
Used for exposure control.

In the embodiment described above, the xyz stage 10 is movable, and the xyz stage 10 is moved in the optical axis direction of the reduction projection lens 8 to measure the focus position (that is, the image plane position) of the projection lens 8 and the wafer 9. Although the positioning is performed, it is also possible to mount the drive mechanism on the projection lens 8 and move the projection lens 8 in the optical axis direction to perform the measurement and the positioning.

At this time, the projection lens 8 and the reticle 7 (and the reticle stage 70) are moved integrally.

Further, instead of detecting the focus position by monitoring the amount of reflected exposure light transmitted from the reference reflection mirror 17 provided on the xyz stage 10 through the reticle 7, the reference reflection mirror and another TTL are used.
Autofocus system (for example, Japanese Patent Application Laid-Open No. Sho 56
-130707 publication. ) May be used to detect the focus position.

Further, in each of the above embodiments, a part of the circuit pattern of the reticle 7 is used to guide the predetermined light to the reference reflection mirror 17, but a pattern (window) for focus position detection is separately provided.
It may be formed on the top and used.

Further, in each of the above-described embodiments, a reference reflection mirror (surface) 19 different from the wafer 9 is provided in the xy direction in order to handle processes such as multilayer resist.
Although provided on the z stage 10, if the reference reflection mirror 19 is not provided, a dummy wafer not coated with resist is used instead of the wafer 9 coated with resist.
It is also possible to mount it on the stage 10 and detect the focus position of the projection optical system by the method described above.

Various forms of the projection exposure apparatus other than those shown in the above embodiment are conceivable. The invention applies.

<Effects of the Invention> As described above, according to the present invention, a predetermined reference reflecting surface is provided on the wafer stage without using a wafer coated with a resist, and the reflecting surface is used to project by a TTL autofocus system. The focus position of the optical system (that is, the image plane position) is detected, and the wafer surface is positioned at the image plane position with this as a reference. Therefore, the focus position of the projection optical system, which changes over time, is accurately detected, and highly accurate focusing is achieved. It will be possible. This has an excellent effect that a high resolution pattern can be formed on the wafer and a circuit with a higher degree of integration can be created.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a projection exposure apparatus having an automatic focus control device according to an embodiment of the present invention. FIG. 2 and FIG. 3 are views showing the state of reflected exposure light from the reference plane mirror when the reference plane mirror and the focus plane of the reduction projection lens coincide with each other and deviate from the focus plane, respectively. . FIG. 4 is a diagram obtained by shifting the position of the aperture stop and shifting the pattern area used for focus detection in FIG. 1. FIG. 5 is a diagram showing the relationship between the output of the focal plane detection system and the autofocus measurement value. FIG. 6 is a flow chart showing the sequence from the focal plane detection to the exposure. FIG. 7 is a configuration diagram when the present invention is applied to a projection exposure apparatus having an illumination area changing mechanism. 1 …… Mercury lamp 2 …… Elliptical mirror 3 …… Optical integrator 4 …… Condenser lens 5 …… Mirror 6 …… Field lens 7 …… Reticle 8 …… Reduction projection lens 9 …… Wafer 10 …… xyz Stage 11 …… Auto focus projection system 12 …… Auto focus detection system 13 …… Imaging lens 14 …… Aperture stop 15 …… Condenser lens 16 …… Light receiving element 17 …… Reference plane mirror 18 …… Focal plane detection System 19 …… Auto focus control system 20 …… Drive system 21 …… Shading pattern 22 …… Transparent part 23 …… Condenser lens 24 …… Beam splitter 25 …… Illumination area variable mechanism 26 …… Imaging lens 27 …… Mirror 28 …… Condenser lens 50 …… Photoelectric detector 51 …… Filter 52 …… Condenser lens 55 …… Filter 56 …… Shutter 220 …… Slice level

Claims (1)

[Claims] 1. A pattern formed on a first object,
In a projection exposure apparatus for projecting onto a second object via a projection optical system, a movable stage holding the second object; a reflecting surface provided on the movable stage; the pattern via the projection optical system; Means for directing light on a reflecting surface; a light quantity detecting means for receiving light from the reflecting surface via the projection optical system and the pattern and detecting a light quantity; based on a signal from the light quantity detecting means Projection exposure apparatus, comprising means for detecting a focus position of the projection optical system.